Fat, energy and breast cancer

Rates of breast cancer vary approximately fivefold among countries and are strongly correlated with national per capita availability of dietary fat. However, this relation may be substantially confounded by many other factors associated with affluent lifestyles, such as reduced parity and physical activity. In large prospective epidemiologic studies, little evidence has been seen to support any major positive association between dietary fat and risk of breast cancer over the range of 15-45% or more of energy from fat. The observation that women in counties in China consuming approximately 25% of energy from fat have much lower rates of breast cancer than U.S. women with similar fat intakes provides additional evidence that factors other than dietary fat account for the large international differences. Some epidemiologic evidence suggests that monounsaturated fat and olive oil in particular may reduce risk of breast cancer when substituted for other types of fat. In contrast to findings for dietary total fat, most types of epidemiologic studies provide indirect support for a protective effect of energy restriction and reduced growth rates against breast cancer, which is consistently observed in animal studies of mammary carcinogenesis.